Various sampling techniques have been proposed for small body missions. These sampling techniques are associated with mission architectures. Mission architectures include lander, harpoon, dart, and touch-and-go (TAG).
Lander Architecture Mission.
In a lander architecture mission, a spacecraft would land and anchor to the surface of a planetary or moving object, and then a sampling tool would be deployed to the surface to acquire a sample. The lander architecture mission allows for the sampling process to take longer than for other mission architectures. For example, the Rosetta mission is a lander architecture in-situ sampling mission to comet 67P/Churyumov-Gerasimenko. The mission was launched by the European Space Agency in 2004 and arrived at the comet in August 2014. Its Philae robotic lander was planned to separate from the Rosetta orbiter spacecraft, land on and anchor to the comet, and then deploy a drill to acquire samples for in-situ analysis. The sampling drill weighs 5 kg, can penetrate up to 250 mm, and can acquire samples at predetermined depths inside its drill bit. The samples can then be transported to a carousel with 25 ovens. The drill was designed to penetrate material with strength ranging from fluffy snow to materials with a strength approaching a few MPa.
Harpoon Architecture Mission
In a harpoon architecture mission, a spacecraft would maneuver to the proximity of a small body surface, e.g., 10 m to 1 km from the surface. A sampler would then be shot to the surface with a tether connecting the sampler to the spacecraft. The momentum of the sampler would embed the sampler into the surface driving the material into the sampler. The sampler would then be ejected from the surface, and would be reeled back to the spacecraft with the tether. However, controlling the tether may be challenging.
Dart Architecture Mission
The dart architecture mission is similar to a harpoon architecture mission, except that there is no tether connecting the sampler to the spacecraft. In the dart architecture mission, the sampler is shot to the surface, and the sampler's kinetic energy is used to drive the sampler into the surface. A sample canister is then ejected from the surface, and the spacecraft would rendezvous with and capture the sample canister.
While the dart architecture mission eliminates the problems associated with controlling a tether, the dart architecture mission adds complexity of tracking, rendezvous, and capturing of the sample canister.
Tag Architecture Mission
In a TAG architecture mission, a spacecraft maneuvers within a few meters of the small body surface, and a robotic arm deploys a sampling tool to the surface. The sample in a TAG architecture mission is quickly acquired, and the spacecraft is then thrusted away. The sample can then be transferred to the spacecraft using the robotic arm.
Thus, a sampling technique for the TAG architecture mission may be beneficial.